German patent documents nos. 100 09 149 and 100 38 343 discuss methods for coding and decoding objects in a traffic route network. With the aid of these methods, geographic objects of any complexity may be referenced and imaged in a navigation system. With these methods, transition points between different navigation maps may be found to enable a changeover between two navigation maps.
Hitherto, however, it is believed that no solution has been known from the existing art with which the changeover between two navigation maps can be performed easily and reliably.
Proceeding therefrom, the exemplary embodiment and/or exemplary method of the present invention is to provide an improved navigation system for a motor vehicle and an exemplary method for operating a navigation system.
This problem may be solved in that the navigation system cited initially is developed by way of the features of the exemplary embodiments and/or exemplary method described herein.
According to the exemplary embodiment and/or exemplary method of the present invention, the point in time for changing over the navigation maps is selected in such a way that during the changeover operation, a deviation of the motor vehicle from the route segment currently being traveled is improbable based on the current navigation data of the motor vehicle. This ensures that during the changeover operation, no data necessary for modification of the navigation route need to be displayed to the vehicle occupant. This increases destination guidance reliability.
According to an exemplary embodiment and/or exemplary method of the present invention, this is done by ascertaining, from a navigation route of the motor vehicle ascertained by the navigation system, a route segment of the navigation route that is free of turns. From a length of the turn-free route segment and from a maximum speed permissible for that route segment and/or the current vehicle speed, an expected travel time of the motor vehicle on the route segment is then ascertained. This ascertained travel time of the motor vehicle is compared with a time necessary for the changeover operation between the navigation maps (data loading, position finding on the new navigation map, route search, etc.), including the storage device changeover operation that may be necessary, and the changeover operation is initiated when the ascertained travel time of the motor vehicle on the route segment is greater than the time necessary for the changeover operation. This permits a reliable changeover between the navigation maps and memory device(s), with no negative effect on destination guidance.